1. Field of the Invention
This invention relates to a technique of manufacturing seamless capsules, and particularly to a method of manufacturing seamless capsules manufactured by use of droplets formed by blowing a liquid flow out of a nozzle, and an apparatus therefor.
2. Related Art Statements
Out of the techniques of manufacturing capsules with no seams in coating layers thereof, i.e., seamless capsules, particularly as a technique suitable for manufacturing capsules smaller in size than an ordinary soft capsule and larger in size than a microcapsule, such a method is widely known that a multi-layer liquid flow is blown out into air or liquid from a multiple nozzle such as a double nozzle and a triple nozzle to form multi-layer droplets, and the outermost layer liquid of the multi-layer droplets is caused to react with hardening liquid, to thereby obtain a seamless capsule, in which liquid in an layer is enclosed.
Furthermore, there has been used such a method that outer portions of single layer droplets, which are formed by use of a single nozzle, are solidified in hardening liquid, to thereby manufacture a seamless capsule of a single layer.
In the techniques of manufacturing the seamless capsules as described above, the outermost layer liquid of the multi-layer droplets for forming the seamless capsules is solidified, namely, hardened, by chemical reaction with a hardening liquid or by cooling with a hardening liquid. In either one of solidifying mechanisms, the droplets solidify gradually as the time for contacting the hardening liquid elapses.
Then, particles of the multi-layer droplets thus solidified are delivered to the following processes where they are separated from the hardening liquid and dried. However, if the solidifying is insufficient, then such unfavorable phenomena occur that the particles are deformed, the particles adhere to each other to agglomerate or solidified membranes are broken.
Accordingly, in order to obviate the above-described disadvantages, the time of contact between the hardening liquid for solidifying the particles and the multi-layer droplets should be satisfactorily lengthened. Particularly, in the case of the solidifying mechanism where solidifying is effected by cooling, the solidifying velocity is slow, so that the time of contact for solidifying should be extended.
Then, it is conceived that, in order to lengthen the above-described contact time, the flow velocity of the hardening liquid should be slowed down.
However, because of the following problems (A) and (B), it is difficult to adopt the lengthening of the time of contact by slowing down the flow velocity of the hardening liquid.
(A) In order to prevent the breakage and deformation of the droplets, a relative velocity between the multi-layer droplets blown out of the nozzle and the flow of the hardening liquid should be reduced as much as possible. As the velocity of the hardening liquid is slowed down, the blow-out speed of the droplets should be reduced accordingly, thus lowering the producing efficiency. PA0 (B) Even when the above-described problem (A) is solved by some method, the density of the droplet particles in the hardening liquid is increased, and thus adhesion of unsolidified droplets tends to occur easily.
Therefore, it has heretofore been conceived that the length of a course for conveying the droplets from the contact of the multi-layer droplets with the hardening liquid to the reach of the droplets to a separating device is satisfactorily lengthened structurally, thus securing the contact time.
However, this conventional structure has the disadvantage that the apparatus is largely increased in size, particularly, in the case where the capsules is solidified with cooling liquid, thus presenting one of the difficult problems of the apparatus for manufacturing seamless capsules under the method of solidifying the multi-layer droplets.